Heat exchanger



Dec. s, 1936.

v F. M. HARDIMAN ET AL HEAT EicHANGER v Filed March 8, 1955 rllllllll Il Pefenged Dee. s, 193e PATENT OFFICE HEAT EXCHANGE!! Frank 1u. nudimnn and Laurence r. Saunders, Lockport, N. Y., assignors to General Motors Corporation, Detroit, Mich., a corporation of ,'Delaware Application M s, 1935,v semi ne.' asas 2 claims. (c1. 251-262) Unit heaters for attachment in a building heating system with a motor driven fan to direct room air pver a number of steam pipes, as well as other types of heat exchangers, generally make use of a iin and tube type radiator. The several `finned tubes form a core and extend in spaced relation between a pair of headerspr tanks for connection with the steam or inlet pipe and condensate or return pipe, respectively, and air passing over the exposed radiating surface carries away heat. g

An object of the present invention is to provide a finned tube which will be highly efficient in the transfer of heat in that the ns will rapidly 'adsoz'b heat from thetube containing heating medium and handle the air passing through the core to insure wiping contact of a large number of air particles. 4 y

A further and important object is to provide a o iin assembly of simple design from the manufacturing standpoint so that production may be accomplished easily and quickly and at low cost.

The above and other objects and advantages of the inventionwill become apparent during the 25 course of the following specication taken in connection with the accompanying drawing, wherein Figure 1 is a front elevation of a unit heater; Figure 2 is an elevation of a fragment of one vof the finned tubes on an enlarged scale;

30 Figure 3 is a detail perspective view of a n strip after having been formed, but prior to bending to shape; Figures 4 and 5 are detail sectional views taken on lines l-I and 5 5, respectively, of Figure 3, and Figure 6 is a section through the 35 tube shown of a slightly modified type of iin.

A preferred, but not necessarily the only embodiment of the invention, is illustrated. Shown in Figure 1 is a unit heater assembly which includes a top tank o`r inlet header and a bottom .40 tank or outlet header 2 with an intermediate core In this view the tube -fragment 4 extendsu through a number of spaced fins 5 formed from a continuous strip folded upon itself to-substan tially zigzag shape. Each iin, therefore, has connecting portions 6 6 at opposite ends extending in opposite directions and joining next succeeding fins. That is to say, each fin has a laterally extending portion 6 at one side connecting it to the n above and an angularly bent portion 6 at the other side connecting to the fine below. The sev- 'L eral connecting portions 6 6 serve to space the fins 5 5 apart and the iins are additionally spaced apart by annular iianges or collars 1 projecting laterally and dening tube receiving openings through the fins.

The collars extending between the iins coop- 5 erate to form a substantially continuous tubelike wall in which the main tube I is nested in close tting relation. If desired, the several collars may be secured to the tube as by solder, welding or the like, although reliance may be placed lo p merely on the frictional surface contact for holding the ins against displacement. At arrv rate e the collars provide a large area of tube contacting surface which facilitates the flow of heat from the tube 4 into the fins 5 5 for dissipa- 15 tion into the air stream.

Increased dissipation is obtained by controlling the direction of air flow in a way t9 insure a maximum number of air particles coming into wiping contact with the nn. This can be accomplished by providing in each iin the series of louveredopenings 8, the action ofwhich will be referred to more in detail later.

In the manufacture of the iin strip a continu- A ous ribbon of thin metal, such as copper or brass, may be formed at regular intervals with a group of formations, as illustrated in Figure 3, and subsequently folded upon itself along transverse lines between succeeding groups oi' formations,

to provide the series of fins. The strip preferably is reversely bent upon itself along opposite longitudinal edges as at 9 to reinforce the edge and stiien the entire strip. At spaced intervals, portions of the 1in material are punched out to provide a longitudinal row of tube receiving open-k ings and the peripheral margin of each of these is formed with a laterally projecting annular iiange which constitutes the collar 1. To facilitate the formation of the pressed out collar, circumferentially spaced slits l2 may be cut at in- 40 vtervals `in the margin of the opening to prevent the material crowding upon itself. l

nIt is to be noted in Figure 3 that alternate collars project outv of the plane of the strip on the same side and that the remaining collars project on the opposite'side of the strip. Since the collars associated with succeeding openings extend in opposite directions and because the strip is folded upon itself in zigzag relation, in the as sembled iin strip all of the collars will extend from the ns in the same direction as is illustrated in Figure 2, where each collar projects below its iin. The folding of .the strip occurs about transverse lines between succeeding tube receiving openings and for the sake of clearo il `ance such lines of bending are indicated in Figure 3 by broken lines which also define the successive sections of the iin strip which constitute the ns.

vered opening will be apparent upon an inspec- A tion of Figure 5 and considering this gure for the moment, if the air streams wiping opposite sides of the iin are considered as moving toward the left those particles wiping the underside of the right-hand end of the iin will ride down the inclined under surface of the bale il and move into space at the slit and similarly those air particles wiping the upper side of the n move down the inclined upper surface of the deector and then into a non-wiping strata. The two deiiectors I0 and il cooperate in shifting the air stream and the leading edge of the deflector I0 serves to divide the stream and the divisions, having previously been in a non-wiping strata, now come into contact with the opposite sides of the n. By employing several of such chuted openings in the`n there will occur severalnchanges in the relation of air particles to the iin, whereby a large number of air particles will be brought into wiping engagement with the fin surface-and more work is obtained from a givenA number of particles. i

Somewhat increased dissipation canbe secured by offsetting the row of tube receiving openings from the longitudinal center line of the strip and presenting the widest side of the iin to the incoming fresh air. A single iin having an offset tube opening is illustrated in Figure 6 and from this view it Willbe seen that most of the n is directly exposed to unrestricted iiow thereacross of the air stream and only a small portion at the rear obstructed by the tube. Otherwise the iin is as heretofore described and forms an integral part of a continuous zigzag strip.

We claim:

1. In a iin and tube radiator, a n strip comprising a continuous ribbon having a seriesof spaced openings therein and being reversely folded at intervals to provide a series of spaced ns with said openings in alinement to receive a tube, each n having therein a series of circumferentially spaced slits in radial relation to the opening in the n, with the material immediately adjacent and on opposite sides of each slit pressed in opposite directions out of the plane of the iin for cooperation in providing an inclined chuted opening through the iin.

2.v In a n and tube heat exchanger, a continuous fin strip having succeeding portions thereof in right angular relation to each other so that alternate portions lie in parallel planes with one set of alternate portions constituting superposed fins spaced apart by the other set, reinforcing formations on the leading and trailing longi- -tudinal edges of the strip, each n portion being further stiffened by a lateral ange dening a tube embracing opening and by a series of circumferentially spaced formations, each comprising oii'set. scoops pressed in opposite directions from the iin on opposite sides of a line slit, with the lines of adjacent slits angularly related to each other.

FRANK M. HARDIMAN. LAURENCE P. SAUNDERS. 

